Tertiary trialkylamine

P-450 amine dealkylation mechanisms. Because kn/ko values for A -demethylation of / -substituted A, A -dimethylanilines by cytochrome P-450 are nearly identical with those for the hydrogen abstraction reactions of t-BuO , it was proposed that P-450 reacted by a direct hydrogen-atom-abstraction mechanism (B) rather than a sequential electron-proton-electron-transfer mechanism (A) [78, 80]. Identical relationships between A h/ d values for reactions of t-BuO and P-450 has been expanded for other substrates including />-xylene, toluene, benzyl alcohol, and tertiary trialkylamine [78]. It has thus been suggested that all these P-450 reactions proceed by a common hydrogen-atom transfer mechanism [78]. 

Melt reaction mechanisms of tertiary aliphatic amine catalyzed phenolic-epoxy reactions were proposed to begin with a trialkylamine abstracting a phenolic hydroxyl proton to form an ion pair (Fig. 7.36). The ion pair was suggested to complex with an epoxy ring, which then dissociated to form a /1-hydroxycther and a regenerated trialkylamine.87... 

The relationship between the structure of the tertiary amine and the intrinsic rate of racemization was clear. This effect has been studied before by Williams,[32 among others. Two families of bases were compared trialkylamines and 4-alkylmorpholines. The trends were most clearly expressed in the experiments using Boc-Ser(OBzl)-NCA. The rate was decreased within each family as the steric bulk of the amine was increased. This result was consistent with the direct enolization mechanism that requires a close approach of the tertiary amine for the abstraction of the a-proton. The rate was much lower with 4-alkyl-morpholines than with trialkylamines because of the decreased basicity of the former (triethylamine and 4-ethylmorpholine have similar structures TEA is actually more hindered). The most favorable results with respect to racemization were obtained when a weak base was combined with a sterically hindered substituent, as with 4-cyclohexylmorpholine. In the case of Boc-Phe-NCA, the same trends were seen, except that racemization by the 4-alkylmorpholines was so slow that the differences within that family were not significant. 

Deoxygenation of amine oxides. Trialkylamine N-oxides and dialkylarylam-ine N-oxides are converted to the tertiary amines on reaction with this anhydride in CH2C12 at 25°.1... 

Leland and Powell also studied ECL obtained from reaction of [(bpy)3Ru]3+ with trialkylamines [47], Since the mechanism involves an electron transfer from the amine to Ru3+, there exists an inverse relationship between the first ionization potential of the amine and ECL intensity. The relative intensity of [(bpy)3Ru]2+ ECL was found to be ordered tertiary > secondary > primary. Quaternary ammonium ions and aromatic amines do not produce ECL with Ru(II) diimine complexes. Brune and Bobbitt subsequently reported the detection of amino acids by [(bpy)3Ru]2+ ECL [28,29], Employing capillary electrophoresis for separation, the presence of various amino acids can be detected directly by reaction with [(bpy)3Ru]3+ generated in situ with up to femtomo-lar sensitivity and with a selectivity for proline and leucine over other amino acids. The formation of an amine radical cation intermediate is characteristic of proposed mechanisms of both aliphatic amines and amino acids. 

Our experience with tributylamine shows that its cathodic potential limit may be as low as 0 V Li/Li+. The cathodic limiting reaction may be the reduction of the cation (for alkaline metals and TAA salts). We have evidence that tributylamine reacts with lithium to form amides (RjNLi, 0 < x < 2, ldeposition potentials of the alkaline metals are reached, trialkylamine solvents will react with the deposits. The anodic limit of most of the trialkylamines, as well as of secondary amines, is in the 3.5-4 V range versus Li/Li+. The reaction is probably the formation of tetraalkyl ammonium cations, protons, and nitrogen. Hence, the electrochemical limit of amines may range between 2-4 V (higher for the tertiary amines). 

Ruff et al. in a series of publications described the synthesis of amine complexes of aluminum hydride [32, 33]. Their study investigated the reaction of these materials with typical Lewis bases in order to define the conditions for the stability of aluminum hydride derivatives in which the aluminum atom exhibits a coordination number of five. They first described methods for making tertiary alkyl amine complexes of aluminum hydride utilizing lithium aluminum hydride and an amine hydrochloride. A finely ground lithium aluminum hydride was placed together with trimethylammonium chloride (ratio 1 2). They prepared other trialkylamine alanes and the N-dialkylaminoalanes, in a similar fashion. These adducts of alane were found to sublime readily at temperatures up to 40 °C except for the tri-n-propylamine alane, which sublimed very slowly and could also be recrystallized from hexane at — 80 °C. 

As discussed earlier, deprotonation of a-carbon forms a major reaction pathway for the disappearance of the amine radical cation. Studies of photoinduced electron-transfer reactions of tertiary amines by Lewis [7, 11] and by Mariano [5, 10] have contributed significantly towards our understanding of the factors that control this process. Lewis and coworkers used product-distribution ratios of stilbene-amine adducts to elucidate the stereoelectronic effects involved in the deprotonation process [5, 10, 121, 122]. In non-polar solvents, the singlet excited state of tran -stilbene forms non-reactive but fluorescent exciplexes with simple trialkylamines. Increasing solvent polarity brings about a decrease in the fluorescence intensity and an increase in adduct formation. For non-symmetrically substituted tertiary amines two types of stilbene-amine adduct can be formed, as is shown in Scheme 9, depending on whether the aminoalkyl radical adding to the stilbene radical is formed by de-... 

Although aryl halides and triflates are the most commonly used arylating agents, there are successful examples where both aroyl chlorides and arylsulfonyl chlorides have been employed. Pd-catalyzed decarbonylations and desulfonylations and subsequent Heck couplings are often conducted with trialkylamines such as A-ethylmorpholine as a base, but improved yields are reported in cases in which the tertiary amine is replaced by a mixture of potassium carbonate and benzyltrioctylammonium chloride. In Table 2 two examples are given (entries 17 and 18). ... 

Secondary and tertiary alcohols can be silylated under mild conditions using Et3SiOTf and 2,6-lutidine or a trialkylamine as a proton scavenger (eqs 1 and... 

Rapid growth of urethane technology can be attributed to the development of catalysts. Catalysts for the isocyanate-alcohol reaction can be nucleophilic (e.g., bases such as tertiary amines, salts and weak acids) or electrophilic (e.g., organometallic compounds). In the traditional applications of polyurethanes (cast elastomers, block foams, etc.) the usual catalysts are trialkylamines, peralkylated aliphatic amines, triethylenediamine or diazobiscyclooctane (known as DABCO), N-alkyl morpholin, tindioctoate, dibutyl-tindioctoate, dibutyltindilaurate etc. 

The dichromate oxidation of tertiary alkyl aryl amines in a sulfate-bisulfate buffer was found to give secondary amines in good yields. Trialkylamines did not react under the conditions used,... 

Ytterbium triiodide activates the C-F bond of alkyl fluorides giving iodides in high yields (82-98%) in CH2CI2 or CHCls. The reaction is successful in the presence of ketone, ether, alcohol, ester, trialkylamine, aryl, and cyano groups in the substrate and with primary, secondary, and tertiary fluorides but does not occur with polyfluorinated compounds, or those with a CF2, CF3, or group. The reaction... 

In addition, Halcomb and Freeman-Cook have shown that replacing the standard trialkylamine base with 2,6-di-t-butylpyridine can permit the selective protection of a primary hydroxyl over secondary and tertiary hydroxyls (eq 21). ... 

Tertiary amines, unlike their phosphine analogues, enter into a variety of reactions depending upon their overall structure. Van Alphen examined the reaction of triethylamine with MA. An impure black substance was isolated which was soluble in water and released triethylamine on treatment with alkali. Mayahi and El-Bermani have observed a very exothermic reaction on mixing the same reactants neat. However, they also observed a clear yellow solution initially a dark brown solid was isolated. Based on spectroscopic evidence such as IR, NMR, and UV of the product, they rationalized their observations as follows At first, a charge-transfer complex 1 forms on mixing the reactants (a yellow solution). The tt complex 1 then collapses to the dark-brown product 3 through an intermediate cr complex 2. The intermediacy of 1 is important since succinic anhydride forms no complex or coloration with TEA. Spontaneous polymerization of MA in the presence of pyridine and trialkylamine has been reported.Zwitterionic cyclic intermediates are proposed. 

Titanium enolates have also been obtained by direct deprotonation from ketones and imides upon treatment of titanium tetrachloride in the presence of tertiary amines, preferably, Hiinig s base. As they have been found to be efficient in syn-selective aldol additions [120], their configuration has been assumed to be cis, but they were rarely characterized by NMR spectroscopy. For the titanium enolate derived from Evans-type auxiliaries, the relative ratio of base to titanium tetrachloride was found to have a distinct impact on the selectivity in the addition to aldehydes. This effect has been rationalized by postulating an equilibrium between the tetrachlorotitanate 106/titanium tetrachloride and the titanium enolate 107/pentachlorotitanate, as supported by NMR studies (Scheme 2.30) [121]. Several chiral ketones have been converted into the corresponding cis-enolates by treatment with TiClgOiPr in the presence of Hiinig s base [122]. Titanium tetrachloride and trialkylamines also lead to aldehyde enolates and enable directed aldol additions between aldehydes. This is remarkable in view of the fact that preformed enolates of aldehydes are not readily accessible [123]. 

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